Dewaxing solvent for mineral oils



Patented Dec. 1, 1942 UNlTED STATES PATENT OFFICE DEWAXING SOLVENT FOR MINERAL OILS Luke B. Goodson, Phillips, Tex., James V. Montg omery,

Okmulgee and Robert W.

Henry,

Bartlesville, Okla... assignors to Phillips Petroleum Company, a corporation of Delaware No Drawing. Application October 28, 1940, Serial No. 363,208

3= Claims.

' atom, such as aliphatic, cyclic, or aromatic thioalcohols, thioethers, thioketones, and thioesters are good dewaxing solvents in that they are completely miscible with the waxy oil at elevated temperatures and have a high solubility for the oil component and a low solubility for the wax component at dewaxing temperatures particularly at temperatures of F. and below.

An object of this invention is to provide an improved solvent for use in the dewaxing of mineral oils.

Another object of this invention is to make use of a certain class of sulfur containing organic compounds in the solvent dewaxing of mineral Still another object of this invention is to provide a dewaxing solvent which may be used in connection with wax anti-solvents.

.Still other objects and advantages will be apparent from a study. of the disclosure which follows.

These above mentioned types of organic sulfur compounds may be used in a wide range of solvent to oil ratios, depending in some measure upon the particular compound employed and upon the method of separating the wax from the chilled solvent oil solution. We have found that 3 to 1 solvent to oil ratios give good results. These waxy oil-solvent solutions may be slow chilled or shock chilled to the required dewaxing temperature. Either method of chilling in the presence of our improved dewaxing solvent gives distinct and sharp edged wax crystals which permit rapid and efiicient filtration. For example, wax precipitated by shock chilling in Carbondale chillers from a 3:1 solvent to oil solution gave a good filter rate. The advantages of shock chilling over slow chilling are readily understood by those skilled in the art.

The application of our invention will give substantially wax free oils having pour points well within the range of effectiveness of pour point '55 depressants such as Parafiow, etc. Furthermore, the use of known wax anti-solvents with these compounds gives oils of practically the same pour point as the dewaxing temperature.

The following examples serve to demonstrate the utility of our invention.

Example 1 One volume of treated waxy Mid-Continent lubricating oil stock of '70 seconds Saybolt universal viscosity at 210 F. was mixed with three volumes of diamyl sulfide and the mixture heated to 150 F. to insure complete solution. The oilsolvent solution was then shock chilled to 0 F. in a Carbondale chiller to precipitate the wax and filtered in the conventional manner. The sulfide solvent Was removed from the oil by distillation and gas stripping leaving an oil which had a pour point of 35 F.

Ewample II One volume of treated waxy Mid-Continent lubricating oil stock of seconds Saybolt universal viscosity at 210 F. was mixed with three volumes of amyl mercaptan and the whole heated to F. as in Example I. The resulting solution Was shock chilled to 0 F. and filtered. The solvent was removed as previously described and the resulting oil had a pour point of 30 F.

This invention is not to be limited in any man ner by the above given examples which are listed for illustration only. It is to be understood that the homologs of these compounds are closely related in physical and chemical properties and that any of the said homologs which exist in suitable boiling point range as to permit separation from the oil and wax and within suitable melting point range as to remain in the liquid state at dewaxing temperatures, are suitable within degree as dewaxing solvents. Among these homologs and other sulfur bearing compounds which are useful as dewaxing solvents may be listed:

normal propyl mercaptan, iso-propyl mercaptan,

butyl mercaptan, hexyl mercaptan, heptyl mercaptan, cyclo propyl mercaptan, cyclo butyl mercaptan, cyclo amyl mercaptan, cyclo hexyl mercaptan, cyclo heptyl mercaptan, methyl sulfide, ethyl sulfide, methyl-ethyl sulfide, propyl sulfide, butyl sulfide, carbon disulfide, methyl thiocyclo propane, methyl thiocyclo butane, methyl thiocyclo pentane, methyl thiocyclo hexane, methyl thiobenzene, ethyl thiobenzene, mono, di, and tri-thio phenols, mono, di, and tri-thio cresols, etc.,'or mixtures of the above compounds, such as caustic oils or selected fractions of caustic oils which result from the treating of sour petroleum distillates with caustic, or from acid sludge which results from acid treatment of petroleum distillates containing sulfur compounds.

These above-mentioned compounds when used with wax anti-solvents such as acetone, methylethyl ketonc, diethyl ketone, dipropyl ketone, dibutyl ketone and other aliphatic ketones, such as mixed ketone, pyridine, picolines, furfural, aniline, nitrobenzene, etc., give exceptionally good results as dewaxing agents. These sulfur containing compounds in most cases are sufficiently good oil solvents and have sufliciently low melting points that the addition of a third component, such as toluol in the benzol-acetone process, to lower the miscibility temperature or to prevent crystallization of the solvent is unnecessary. This point is a decided advantage since it is much easier to control a two-component solvent than one containing three components.

The following examples illustrate the use of solvents composed of mixtures of our organic sulfur compounds with wax anti-solvents.

Example III One volume of treated waxy Mid-Continent lubricating oil stock of '70 seconds Saybolt universal viscosity at 210 F. was mixed with three volumes of solvent composed of 60% amyl mercaptan and 40% acetone. The components were mixed thoroughly to insure complete solution, shock chilled to 0 F. in a Carbondale chiller, filtered and the solvent removed by distillation.

to 120-140 F. The mixture is then chilled to the dewaxing temperature, say 0 F., in essentially any type of chilling apparatus available, and filtered in any suitable type of filter. Filtration is usually rapid since the wax crystals formed in our solvent are distinct and sharp edged. The slack wax may be washed with additional solvent mixture at the dewaxing temperature to remove the adhering oil-solvent solution, while the combined filtrate solution and washings comprising dewaxed oil and solvent mixture are conducted to a solvent-oil separating apparatus. This separating apparatus may comprise a conventional pipe heater and fractionator from which the solvent mixture is removed overhead as vapors and the oil exits from the lower portion thereof and is conducted to storage. The solvent vapors from the above-mentioned fractionator are condensed and the condensate conducted to intermediate storage preparatory to reuse.

The above-given solvent combinations and solvent concentrations may be varied and used in The resulting dewaxed oil had a pour point of Example IV One volume of the waxy oil used in Example III was mixed with three volumes of a solvent composed of 70% diamyl sulfide and 30% acetone. The solution was mixed thoroughly, shock chilled to 0 F. as above, filtered, and the solvent removed by distillation. The oil resulting from the treatment had a pour point of 10 F.

In carrying out our invention, we do not wish to be limited by any special type of dewaxing apparatus, since essentially any standard dewaxing equipment should be satisfactory. For dewaxing of the above mentioned Mid-Continent oil stock,

. the oil to be dewaxed is mixed with the sulfur containing organic compound, as for example diamyl sulfide or amyl mercaptan with or without a wax anti-solvent, and the mixture warmed gently to insure complete and rapid solution, say

many ways as will be readily understood by those skilled in the art without departing from the spirit of our invention, and we do not wish to be limited in any manner by the afore-given specific examples.

We claim:

1. The process of dewaxing mineral oils including the steps of mixing the waxy oil with a dewaxing solvent comprising amyl mercaptan and a wax antisolvent, in which the antisolvent is acetone, chilling the mixture to precipitate the wax and separating the precipitated wax.

2. The process of dewaxing mineral oils including the steps of mixing the waxy oil with a dewaxing solvent comprising a major proportion of amyl mercaptan and a minor proportion of a wax antisolvent, in which the antisolvent is acetone, chilling the mixture to precipitate the wax and separating the precipitated wax.

3. The process of dewaxing mineral oils including the steps of mixing the waxy oil with a dewaxing solvent comprising 60 per cent by volume of amyl mercaptan and 40 per cent by volume of a wax antisolvent, in which the antisolvent is acetone, chilling the mixture to precipitate the wax and separating the precipitated wax.

LUKE B. GOODSON. JAMES V. MONTGOMERY. ROBERT W. HENRY. 

